Vapors generated in wood pulp digesting processes of the prior art have been used in various manners. For example, the use of vapor from a digester to heat a processing liquid is disclosed in U.S. Pat. Nos. 1,645,754; 2,041,597 and 2,859,108. The system disclosed in the '108 patent is an acid digestion system which additionally utilizes vapor from a blow tank or blow cyclone as a heating medium to indirectly heat the digesting acid.
U.S. Pat. Nos. 3,530,034 and 3,814,662 disclose the use of heated vapor for pre-heating wood chips. In the '662 patent, the heated vapor originates in a blow tank.
U.S. Pat. Nos. 1,648,111 and 2,999,785 disclose other uses of heated vapor issuing from a blow tank. In the '111 patent, the vapor is used to indirectly heat an evaporator. In the '785 patent, the vapor from the blow tank is used to heat pulp that has issued from the blow tank and also to heat wash water within a heat exchanger. U.S. Pat. Nos. 2,808,234 and 3,325,970 disclose condensers for condensing vapor issuing from a blow tank.
While the prior art is replete with numerous uses of heated vapors in pulp digesting processes, it is applicants' belief that the pressure controlled use of vapors from a blow tank or blow cyclone to mix with and heat a processing liquid within a pressure accumulator in an alkaline pulp digesting process has not been attempted.